This invention relates to an acid processing system for processing substrates such as silicon wafers in the manufacture of electronic devices, such as integrated circuit chips, and more specifically to the application of a mixture of chemicals to such substrates.
In the manufacture of electronic devices such as integrated circuit chips, an acid processing system is used for processing the substrates such as silicon wafers. The processing of such substrates is a multistep operation and, depending upon the actual processes being carried out, a number of different chemicals are sequentially applied, as by spraying, to the substrates; and each chemical processing step is preceded and followed by a rinsing step using a rinsing liquid, such as water. During certain of the processing steps during which liquid chemicals are being applied to the substrates or wafers, two or more different liquid chemicals are applied to the substrates simultaneously. In the known processes, the procedures followed have required that the liquid chemicals be mixed, as in a mixing chamber, located along the supply lines which supply chemicals to the spray post directing the liquid chemicals onto the substrates in the processing chamber.
Some of the chemicals which are mixed together and used in such chemical processing steps for such substrates are highly active and dangerous to handle, especially when mixed with other highly active chemicals. For instance, ammonium hydroxide must be mixed with nitric acid in certain steps involved in the processing of such substrates. In other processing steps, concentrated hydrochloric acid is mixed with hydrogen peroxide. These mixtures of highly active chemicals are typical of those which create dangerous conditions during the mixing of such chemicals together as they are supplied to the processing chamber for spraying onto the substrates.
Other chemicals that must be mixed together in certain processing steps are of a nature as to degrade very quickly and loose their effectiveness shortly after they are mixed together. For instance, ammonium hydroxide is mixed with hydrogen peroxide in certain processing steps, and if this chemical mixture is not applied to the substrates almost instantaneously after mixing, it will begin to degrade with lesser effectiveness, thus affecting the process being carried out.